A series of chilling, never-before-seen letters from John Lennon’s murderer, Mark David Chapman, to Steve Spiro, the NYPD officer who arrested him, reveal a glimpse inside the mind of the deranged killer.

Chapman bizarrely “wanted to be friends” with the cop who was first on the scene at the 1980 shooting and said they were “part of something big.” “Besides wanting to be your friend,” reads the first of three typed letters to Spiro in 1983, “is there any way that you can help me locate my copy of ‘The Catcher in the Rye’ that was taken from me on the night of my arrest?”

Chapman was infamously collared with a copy of the J.D. Salinger novel inscribed with, “This is my statement.” Chapman’s letters to Spiro are being sold through Gary Zimet’s Moments in Time and valued at $75,000.

“I am wondering if you now understand this,” Chapman asks of the inscription in one letter that ends, “You’re probably still the ‘best damn cop in New York City.’ ”

Less than two weeks later, Chapman wrote Spiro: “From the time of my arrest I have felt close to you . . . It is something that would happen to Holden Caulfield.” He adds, “To answer the question of what was meant by ‘This is my statement’ . . . do you remember that young woman in Saigon during the Vietnam war that immolated herself . . . She believed so strongly in her purpose that she chose to end her life rather than continue living in this phony world. Poems were found on her . . . This was her statement. ‘The Catcher in the Rye’ is my statement.”

“We were all part of something big, Steve,” Chapman eerily writes. “Something phenomenal. It is all going to come out.”

He writes in a third letter weeks later: “Lennon was a phony of the highest degree, but there were others who could — and would — have served the same purpose.”

Still in prison for the murder at the Dakota on the Upper West Side, Chapman has been denied parole seven times. The last letter ends with, “Steve, it is all in ‘Catcher in the Rye.’ ”